mutagen/optimfrog.py

   1 # OptimFROG reader/tagger
   2 #
   3 # Copyright 2006 Lukas Lalinsky <lalinsky@gmail.com>
   4 #
   5 # This program is free software; you can redistribute it and/or modify
   6 # it under the terms of the GNU General Public License version 2 as
   7 # published by the Free Software Foundation.
   8 #
   9 # $Id: optimfrog.py 3923 2006-10-21 15:07:13Z luks $
  10
  11 """OptimFROG audio streams with APEv2 tags.
  12
  13 OptimFROG is a lossless audio compression program. Its main goal is to
  14 reduce at maximum the size of audio files, while permitting bit
  15 identical restoration for all input. It is similar with the ZIP
  16 compression, but it is highly specialized to compress audio data.
  17
  18 Only versions 4.5 and higher are supported.
  19
  20 For more information, see http://www.losslessaudio.org/
  21 """
  22
  23 __all__ = ["OptimFROG", "Open", "delete"]
  24
  25 import struct
  26 from mutagen.apev2 import APEv2File, error, delete
  27
  28 class OptimFROGHeaderError(error): pass
  29
  30 class OptimFROGInfo(object):
  31     """OptimFROG stream information.
  32
  33     Attributes:
  34     channels - number of audio channels
  35     length - file length in seconds, as a float
  36     sample_rate - audio sampling rate in Hz
  37     """
  38
  39     def __init__(self, fileobj):
  40         header = fileobj.read(76)
  41         if (len(header) != 76 or not header.startswith("OFR ") or
  42             struct.unpack("<I", header[4:8])[0] not in [12, 15]):
  43             raise OptimFROGHeaderError("not an OptimFROG file")
  44         (total_samples, total_samples_high, sample_type, self.channels,
  45          self.sample_rate) = struct.unpack("<IHBBI", header[8:20])
  46         total_samples += total_samples_high << 32
  47         self.channels += 1
  48         if self.sample_rate:
  49             self.length = float(total_samples) / (self.channels *
  50                                                   self.sample_rate)
  51         else:
  52             self.length = 0.0
  53
  54     def pprint(self):
  55         return "OptimFROG, %.2f seconds, %d Hz" % (self.length,
  56                                                    self.sample_rate)
  57
  58 class OptimFROG(APEv2File):
  59     _Info = OptimFROGInfo
  60
  61     def score(filename, fileobj, header):
  62         return (header.startswith("OFR") + filename.endswith(".ofr") +
  63                 filename.endswith(".ofs"))
  64     score = staticmethod(score)